I. Field of the Invention
The present invention is directed to the design of catheter structures for use in the treatment of coronary stenoses or other vascular obstructions, and more specifically to the design of a CTA/CP (coronary transluminal angioplasty/coronary perfusion) catheter assembly or attachment which facilitates the placement of an expander in a blood vessel at the site of an atheromatous lesion for inflation to apply a predetermined pressure on the lesion to dilate same while still permitting communication with the blood vessel at a site distal to the inflated expander member.
II. Discussion of the Prior Art
Obstructive coronary artery disease is generally recognized as a serious health problem in the United States and most of the western world. When drug treatment fails or inadequately controls angina pectoris, coronary artery bypass graft surgery is generally used.
In 1964, C. T. Dotter and M. P. Judkins introduced a transluminal coaxial catheter dilatation method for dilating atheromatous lesions in peripheral arteries. This technique required sequential dilation of stenotic lesions and employed progressively larger dilating catherters. The technique failed to gain wide acceptance, incidences of endothelial damage leading to frequent complications. Then, in 1971, Zeitler, Schoop and Zahnow reported the use of a "Fogarty Balloon Catheter" to perform transluminal arterioplasty. Subsequently, A. Gruntzig, M.D., employed the techniques reported earlier by Dotter, Zeitler and others, using a single double-lumen catheter with a distensible (balloon) segment at its tip which was positioned in the lumen at the stenotic segment of a peripheral artery. The elastic balloon segment was then inflated, resulting in compression of the atheromatous lesion in a manner perpendicular to the vessel wall, thus dilating the lumen. The balloon remained inflated about 10-15 seconds at 7 atmospheres internal pressure and then was deflated. It was found that there was a significant reduction in complications due to endothelial damage, such as that caused by earlier reported coaxial transluminal dilation techniques, and marked improvement in vessel patency through the use of the improved catheter. In a paper entitled "Coronary Percutaneous Translumenal Angioplasty: Preliminary Results" Circulation 57, 58 (Supp. II): II-56, 1978, Dr. Gruntzig presented data on 80 patients suffering from severe angina which data was obtained approximately six months following dilation of occluded coronary arteries using small diameter double-lumen CTA (coronary transluminal angioplasty) catheters. Of the 54 patients out of 80 on whom the dilation was successful, 90 percent indicated a significant pain improvement and patency of the dilated obstructions.
From evidence to date, coronary transluminal angioplasty (CTA) appears to offer a very promising therapeutic technique in symptomatic patients having coronary artery disease. See, for example, "Transluminal Coronary Artery Dilatation" by S. H. Stertzer et al, Practical Cardiology Vol. 5, No. 3, March, 1979. It is believed however, that problems still exist with balloon-tip catheters of the type employed to date for dilatation of atheromatous lesions in coronary arteries (see Editorial Report, Circ., Vol. 60, Page 969, 1979). Specifically, the amount of pressure which can be applied through the balloon-type expander is believed to be insufficient to dilate certain stenotic lesions. Then too, the use of the technique and catheter as presently employed by Gruntzig and others results in a total cessation of blood flow distal to the site of the treatment. In this regard, studies in living dogs with normal coronary arteries have shown that CTA may be associated with brief, self-limited ventricular tachycardia. During the inflation of the balloon, distal coronary pressure falls to zero. Because of the lack of blood flow and pressure distal to the treatment site, the period of dilation must be relatively short to prevent complications due to the lack of a blood supply. It is felt that this short period of dilatation may contribute to the reduction in the success rate of the coronary transluminal angioplasty (CTA) procedure.